Showing image when available - javascript

I am trying to create a web interface for a scientific code. The user will provide some inputs and submit through a HTML form. A php script will take the input and run code on server. In the end of it, one or more (not more than 10) images will be created. The code may take few seconds to hours, depending upon the inputs.
How can I show these images on the webpage after completion, and make them available for download?

You will need to have a method that creates a unique identifier upon completion.
So this can be as simple as checking to see if the image exists, and if not notify the user that it is still in progress.
so something like:
if (file_exists($image_file)) { do something... }
else { echo 'Files still in progress....'; }

Assuming your going todo the scientific code in a background process, the issue would be the frontend.
To make it simple, I would assign the job/calculation a unique url, that relates to the results, much like codepad, viper7, JSFiddle do, then while there on the page poll (AJAX) the server for the images/results. Dont even attempt todo any submitted code, while the user waits or on the request thread.

Related

how to commuincate between php and JS?

I am new to web development and I am trying to build my first website.
I am having some troubles because web development is dependant on several programming languages like PHP and JS, and the most difficult part for me is to communicate between these languages.
For example, I am trying to create a function that compresses a folder and generate a download link to that new archive, this can be easily done by PHP. However, when the user clicks the zip button, I also wish to display a pop-up window that tells the user to wait while the folder is being compressed, and when the compression is done I want to change the text on that pop-up and display the download link, and this, of course, requires JS.
I've tried many solutions but none of them seemed perfect for me, and I feel like that these solutions are quick and dirty, which I don't want.
If there is a secret I do not know, please tell me about so I can finally work with these languages as if they are a single language.
Also, if you can help me with my current problem, I would be extra grateful.
I just want to know how to construct a form that can call the JS function that displays the pop-up, then calls the PHP Zip_Folder function, and once the PHP function is done, I want to display the download link on the pop-up window.
This is my form code: (It only calls the javascript function that displays the pop-up)
<input type = 'button' onclick = 'Show_PopUP(\"Folder_to_zip\")' value = 'Download Folder'>
And this is the Show_PopUP function code:
function Show_PopUP(folder) {
var e = document.getElementById('Folder_Download_PopUp');
if(e.style.display == 'block')
e.style.display = 'none';
else {
e.style.display = 'block';}}
I already have the PHP function that compresses and generate a download link for the archive, so what I need now is a way to call it after the pop-up is displayed, and a way to print the download link on the pop-up once the function is done.
This might not be the best approach since I am a beginner, so if you have suggestions on how to get my task done without this complexity, I would be very happy.
Sorry if my question is too long, and thanks in advance for your help.
What you need to do is use these things called XHRs, or XMLHttpRequest (Google it), from within JavaScript to php, which basically is kind of like an invisible browser going to the php page behind the scenes and "loading" whatever the php page gives back, only this is all happening within JavaScript itself, so you can read that this "invisible page" loaded, which is from php, and do stuff with that, without actually refreshing the page. This process is known as AJAX (look it up)
What you can do is, when you set up this "invisible page", you can also send certain kinds of information along with it that the php page can read, and when it's done the php page can echo something back to the invisible page, which can then be read with JavaScript. This easy you can communicate between php and JavaScript, by sending certain values, in JavaScript, along with this invisible page, and waiting for php to echo something back to it, then reading that with JavaScript
So how do we actually do this?
First on the JavaScript side, we need to make this "invisible page", which is really not technically a page, it just does the sane thing as what is done to display any other web page, which is technically called a "request" since it's like asking the server for some data, it's basically "requesting" it, then when the server echoes something back, that's called he "response" to what was requested
So to make this new request in JavaScript we can do the following
var asking= new XMLHttpRequest ()
now that it as if an invisible page was created, but not yet navigated to anything, but we have to now metaphorically "enter in the URL" to this invisible page (without actually "navigating" to it yet) to do that we do
asking.open("GET", "pathToPHPpage.php?hi=there")
So the first part is called "GET" because we want to simply get a response back, without actually sending anything (if we were sending a file though, we would instead use "POST" then put the file date in the next step), then we enter in the URL to the php page that you want to get. If it's the same as the JavaScript page just put location.href instead, but it's important to add at least something to the end of the URL, notice the "?hi=there", you can call it anything, but it's important to have a question mark immediately following the .php page, then the name of something (in this case"hi") followed by it's value (in this case "there"), because the php page is able to read that, and give a different response back depending on what it says
Ok so now we have to actually "send" that request to the server, which is like metaphorically "navigating" to the URL on the invisible page, to do that
asking.send()
(And if you put "POST" before, you can add the date you want to send in between the parenthesis, usually in the form of a string but it can be different depending on the data, look it up for more reference)
Now, before we continue in the JS side, let's quickly switch over to PHP (doesn't have to be in this order though) to see what happened
We need to listen for any "requests" on the php page, that contain the name "hi" (since that's what we at the end of the URL before), to do that, around the top of PHP (technically anywhere in php though) we do
$isHi = $_GET["hi"];
if(isset ($isHi)) {
//Do some php code
echo "hi back!".$isHi;
}
Basically we just looked for the *hi" name in our "GET" request that was sent to PHP, we checked if it is "set", meaning not nulll, then we echoed some message back to JS, now let's listen for that message on the JavaScript side
Back to JS, after the .send line (or before), we need to listen for when the page echoes back.
To do that we check if it successfully loaded, because sometimes there can be errors, so let's do
asking.onreadstatechange= function () {
if(asking.readyState == 4 && asking.status==200) {
alert(asking.responseText)
} else alert("ooh something happened")
}
Now we have access to the response the php code gave us
You can extend this to other forms of communication, let me know if you have any questions

How to refresh a specific div of a page in PHP?

I am making an online game using PHP and JavaScript, I have more knowledge in PHP than I do in JavaScript, though I am new in both languages, so keep that in mind.
So what I was trying to make in PHP / JavaScript and of course HTML was to refresh only the div or the area of code that I need, and I can't make the page reload every time that it gets new information or data because when the PHP is ran and done then I can't have anything else running, unless I was to use a loop though that sounds a bit sketchy and not sure if that's the method. I have tried: (PHP)
header("reload: 1");
Though that only refreshed the page, that is what I want to happen when I get data not always to be happening, so for example the program would get the information that someone is ready then it would send the client to another page as asll as the other client.
Though I would just like an explination if it is possible to only refresh a specific area when told to by example getting MySQL data.
function refresh_box()
{
$("#myDiv").load('path your PHP file');
setTimeout(refresh_box, 60000);
}
$(document).ready(function(){
refresh_box();
});
this setTimeout call your function for every 1 minute and load content dynamically in mydiv.

Get dynamically changed data from web page using javascript / jquery

I'll be as direct and as specific as possible.
I'm trying to create Greasemonkey addon that would create graph of winnings/loses on: dead link
As you can see, site has front page which dinamicly shows results of wins / loses and how much did which user win/loose. What I'm trying to do is catch every new entry so I can draw some grapsh and or statistics for user / users.
When I access div/span that should have data, it turns out to be empty. I know that reason behind this is that all divs with data relevant to me are empty on load and that they get populated later on.
What I don't know is how to access that data. I can see (using firebug console) that there are GET requests executed all the time and that in those get requests is data that I need.
Can someone tell me or at least point me into right direction, how to access that data every time it gets refreshed / inserted?
You can try using the $.ajaxSuccess function to specify a function in your script to be called everytime an ajax request completes in the main page. This'll be fired for every successful ajax request, whether it pertains to the data you're talking about or not, but should allow you to re-scrape that section of the document to grab any and all data in it after every successful request. You may want to wrap your callback function in a setTimeout of some kind to make sure their own callbacks have a chance to fire and inject/modify the content before you scrape it. It should still seem instantaneous to the user if you set a timeout of, say, 1-10ms.
http://api.jquery.com/ajaxSuccess/

MVC3, switching between Views in the same page

I am working on a MVC project that is supposed to have one page only, with two zones. On one zone I have a Google Map with markers, and the second zone is populated with the selected marker's details.
The details view has a button that when clicked should change the entire view into edit mode without refreshing the page or redirecting it. I have used two views, for details and edit and with the help of ajaxForm function I am switching back and forth between these two views. I'm adding the ajaxForm on documentready for edit view.
<script type="text/javascript">
// wait for the DOM to be loaded
$(document).ready(function() {
// bind 'myForm' and provide a simple callback function
$('#currentDiv').ajaxForm(function(data) {
$('#currentDiv').html(data);
});
});
</script>
The problem appears when on server-side an error appears while trying to save data from edit view and I want to return to the same edit view with the errors displayed. The ajaxForm handler is not added any more and even if the new values that will try to be saved are ok, the detail view is loaded in another page.
Unfortunately, the use of ajaxForm creates some other problems because I don't have control over the cases when the ajax call fails.
Any ideas on how could I fix this? Is it some other solution to switch between those two views without using ajaxForm and without refreshing the page?
I think there are a couple of different questions that you are asking.
First off, you add jquery handlers to deal with the case when you get a 500 type error from the server.
Something like the following. I suggest taking a look at the docs for more info.
$(document).ajaxError(function(event,jqXHR,ajaxSettings,thrownError){
if (jqXHR.status != 0){
window.location = <error page>
}
}
The second problem seems to stem around error handling of known errors (say invalid input). In this case I suggest the following workflow.
1) User clicks on edit button, taken to edit screen
2) User enters in data, use client side validation to do initial check
3) User submits, user is then taken to the view screen and is shown a
success or error message.
The server response could look like:
public ActionResult Edit(EditModel model){
if (!ModelState.IsValid)
{
return Json(new {successful = false, message = "Failed.."});
}
...
}
On the client side, your form callback should now handle the message and the fact it was successful or not. In my implementation, I used knockoutjs to create a "message" area that I could update and clear. (I created templates, etc).
Remember to use client side validation for the easy field validation stuff.... This will save a trip back to the server.
Yours could be quite simple, by popping up the message returned from the server.
Lastly, document ready only fires when the original document is done loading, never again for an ajax call (at least that is my understanding). Just put that code that is the document.ready at the bottom of the edit page. It will fire after the html it is targeting has already been rendered.
Hope that helps!
I have begun to move away from the asp.net views available in ASP.Net MVC due to some incompatibilities and/or unnecessary complexities when trying to achieve functionalities expected of AJAX enabled sites of the day.
I would recommend moving towards a design where you use "dumb" HTML files, use jQuery to download them using AJAX and drop them into a container (personally I use a div) and then use another AJAX call to gather the data from a controller. There are a number of advantages to this approach:
It establishes a real (not fake) separation between client side and server side code.
Html files can be cached on the client cutting down on the amount of data transmitted.
Binding of the Html elements becomes a client side task achieved using jQuery offloading processing cycles from the server.
Controllers essentially become collections of web methods which means they can be untilized by iPhone and Android apps making mobile deployment easier.
I realize this probably isn't the exact answer you're looking for and this may not be an option for you but my hope is that it will help someone at some point make a decision to move away from mixing HTML and server side code.

Alternatives to using meta-refesh for updating a page

In the past, when I've covered events, I've used a meta-refresh with a 5 minute timer to refresh the page so people have the latest updates.
Realizing that this may not be the perfect way to do it (doesn't always work in IE, interrupts a person's flow, restarts things for people with screen readers, etc.) I'm wondering if there's any other way to do handle this situation.
Is it possible to have something like ajax check every few minutes if the html file on the server is newer and have it print a message saying "Update info available, click here to refresh"?
If that's crazy, how about a javascript that just counts down from 5 minutes and just suggests a refresh.
If anyone could point me to tutorials or code snippets I'd appreciate. I just play a programmer on TV. :-)
Actually, your thought on a timed Ajax test is an excellent idea. I'm not sure that is exactly what StackOverflow uses, but it checks periodically to see if other answers have been posted and shows the user, on an interval, if there are updates.
I think this is ideal for these reasons:
It's unobtrusive - the reader can easily ignore the update if they don't care
It won't waste bandwith - no reloading unless the user chooses to
It's informative - the user knows there's an update and can choose to act on it.
My take on how - have the ajax script send off the latest post id to a script that checks for new scripts. This script can query your database to see if there are any new posts, and how many there are. It can return this number. If there are new posts, show some (non modal) message including the number of updates, and let the user decide what to do about it.
setInterval(function() {
if (confirm("Its Been 5 Minutes. Would you like to refresh")) {
window.location.reload(true);
//Or instead of refreshing the page you could make an ajax call and determing if a newer page exists. IF one does then reload.
}
}, 300000);
You can use the setInterval function in javascript.
here's a sample
setInterval("refresh function", milliseconds, lang);
You will use it passing a name to a function that actually refresh the page for the first param and the number of milliseconds between refresh for the second param (300000 for 5 minutes). The third parameter lang is optional
If the user would be interacting with the scores and clicking on things it would be a little rude to just refresh the page on them. I think doing something like a notification that the page has been updated would be ideal.
I would use jQuery and do an ajax call to the file on the server or something that will return the updated data. If it's newer than throw up a Growl message
Gritter - jQuery Growl System
Demo of what a Growl is using Gritter
A Growl message would come up possibly with whatever was changed, new scores and then an option within that message to refresh and view the new results.
jQuery Ajax information

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